// Copyright 2016 the V8 project authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#include "src/compiler/backend/arm/unwinding-info-writer-arm.h"
#include "src/compiler/backend/instruction.h"

namespace v8 {
namespace internal {
    namespace compiler {

        void UnwindingInfoWriter::BeginInstructionBlock(int pc_offset,
            const InstructionBlock* block)
        {
            if (!enabled())
                return;

            block_will_exit_ = false;

            DCHECK_LT(block->rpo_number().ToInt(),
                static_cast<int>(block_initial_states_.size()));
            const BlockInitialState* initial_state = block_initial_states_[block->rpo_number().ToInt()];
            if (!initial_state)
                return;
            if (initial_state->saved_lr_ != saved_lr_) {
                eh_frame_writer_.AdvanceLocation(pc_offset);
                if (initial_state->saved_lr_) {
                    eh_frame_writer_.RecordRegisterSavedToStack(lr, kSystemPointerSize);
                } else {
                    eh_frame_writer_.RecordRegisterFollowsInitialRule(lr);
                }
                saved_lr_ = initial_state->saved_lr_;
            }
        }

        void UnwindingInfoWriter::EndInstructionBlock(const InstructionBlock* block)
        {
            if (!enabled() || block_will_exit_)
                return;

            for (const RpoNumber& successor : block->successors()) {
                int successor_index = successor.ToInt();
                DCHECK_LT(successor_index, static_cast<int>(block_initial_states_.size()));
                const BlockInitialState* existing_state = block_initial_states_[successor_index];

                // If we already had an entry for this BB, check that the values are the
                // same we are trying to insert.
                if (existing_state) {
                    DCHECK_EQ(existing_state->saved_lr_, saved_lr_);
                } else {
                    block_initial_states_[successor_index] = new (zone_) BlockInitialState(saved_lr_);
                }
            }
        }

        void UnwindingInfoWriter::MarkFrameConstructed(int at_pc)
        {
            if (!enabled())
                return;

            // Regardless of the type of frame constructed, the relevant part of the
            // layout is always the one in the diagram:
            //
            // |   ....   |         higher addresses
            // +----------+               ^
            // |    LR    |               |            |
            // +----------+               |            |
            // | saved FP |               |            |
            // +----------+ <-- FP                     v
            // |   ....   |                       stack growth
            //
            // The LR is pushed on the stack, and we can record this fact at the end of
            // the construction, since the LR itself is not modified in the process.
            eh_frame_writer_.AdvanceLocation(at_pc);
            eh_frame_writer_.RecordRegisterSavedToStack(lr, kSystemPointerSize);
            saved_lr_ = true;
        }

        void UnwindingInfoWriter::MarkFrameDeconstructed(int at_pc)
        {
            if (!enabled())
                return;

            // The lr is restored by the last operation in LeaveFrame().
            eh_frame_writer_.AdvanceLocation(at_pc);
            eh_frame_writer_.RecordRegisterFollowsInitialRule(lr);
            saved_lr_ = false;
        }

        void UnwindingInfoWriter::MarkLinkRegisterOnTopOfStack(int pc_offset)
        {
            if (!enabled())
                return;

            eh_frame_writer_.AdvanceLocation(pc_offset);
            eh_frame_writer_.SetBaseAddressRegisterAndOffset(sp, 0);
            eh_frame_writer_.RecordRegisterSavedToStack(lr, 0);
        }

        void UnwindingInfoWriter::MarkPopLinkRegisterFromTopOfStack(int pc_offset)
        {
            if (!enabled())
                return;

            eh_frame_writer_.AdvanceLocation(pc_offset);
            eh_frame_writer_.SetBaseAddressRegisterAndOffset(fp, 0);
            eh_frame_writer_.RecordRegisterFollowsInitialRule(lr);
        }

    } // namespace compiler
} // namespace internal
} // namespace v8
